Use our free online pressure converter to convert between pascals, kilopascals, bar, psi, atmospheres, torr, millimeters of mercury, and other pressure units. Enter a value, select the units, and receive an instant pressure conversion result.
What Is Pressure?
Pressure measures the amount of force applied over a given area. The International System of Units (SI) uses the pascal (Pa) as the derived unit of pressure.
1 pascal = 1 newton per square meter
1 Pa = 1 N/m²
Pressure is measured in many different units because different industries and regions use different standards. Pascals and kilopascals are common in science and engineering, bar is widely used for industrial equipment, psi is common for tire pressure, and hectopascals are frequently used in weather reports.
Common Pressure Units
The most frequently used pressure units include:
- Pascal (Pa): the SI-derived unit of pressure.
- Kilopascal (kPa): equal to 1,000 pascals.
- Megapascal (MPa): equal to 1,000,000 pascals.
- Bar: equal to exactly 100,000 pascals.
- Pound-force per square inch (psi): commonly used for tire, hydraulic, and pneumatic pressure.
- Standard atmosphere (atm): equal to exactly 101,325 pascals.
- Torr: equal to exactly 1/760 of a standard atmosphere.
- Millimeter of mercury (mmHg): commonly used for blood pressure and vacuum measurement.
- Hectopascal (hPa): commonly used in meteorology and equal to one millibar.
Pressure Conversion Formulas
Pressure units can be converted through their equivalent values in pascals. Multiply the original value by its pascal factor, then divide by the pascal factor of the target unit.
Target value = Original value × From-unit factor ÷ To-unit factor
Important pressure relationships include:
- 1 kPa = 1,000 Pa
- 1 MPa = 1,000,000 Pa
- 1 bar = 100,000 Pa
- 1 atm = 101,325 Pa
- 1 Torr = 133.3223684211 Pa
- 1 psi ≈ 6,894.757293 Pa
- 1 hPa = 100 Pa = 1 mbar
Pressure conversion example
To convert 250 kPa to bar:
250 × 1,000 ÷ 100,000 = 2.5 bar
Therefore, 250 kPa equals 2.5 bar.
Pressure Unit Conversion Chart
Use this chart to compare common pressure measurements in kilopascals, bar, pounds per square inch, standard atmospheres, and millimeters of mercury.
| Kilopascal (kPa) | Bar | psi | Atmosphere (atm) | mmHg |
|---|---|---|---|---|
| 1 kPa | 0.01 bar | 0.145038 psi | 0.009869 atm | 7.50062 mmHg |
| 5 kPa | 0.05 bar | 0.725189 psi | 0.049346 atm | 37.5031 mmHg |
| 10 kPa | 0.1 bar | 1.45038 psi | 0.098692 atm | 75.0062 mmHg |
| 20 kPa | 0.2 bar | 2.90075 psi | 0.197385 atm | 150.012 mmHg |
| 50 kPa | 0.5 bar | 7.25189 psi | 0.493462 atm | 375.031 mmHg |
| 100 kPa | 1 bar | 14.5038 psi | 0.986923 atm | 750.062 mmHg |
| 101.325 kPa | 1.01325 bar | 14.6959 psi | 1 atm | 760 mmHg |
| 200 kPa | 2 bar | 29.0075 psi | 1.97385 atm | 1,500.12 mmHg |
| 500 kPa | 5 bar | 72.5189 psi | 4.93462 atm | 3,750.31 mmHg |
| 1,000 kPa | 10 bar | 145.038 psi | 9.86923 atm | 7,500.62 mmHg |
Values are rounded for readability. One standard atmosphere equals exactly 101.325 kPa, while conversions involving psi and mmHg may require additional decimal places for precision.
Pressure Conversion Reference
| Pressure unit | Equivalent in pascals |
|---|---|
| 1 pascal (Pa) | 1 Pa |
| 1 hectopascal (hPa) | 100 Pa |
| 1 millibar (mbar) | 100 Pa |
| 1 kilopascal (kPa) | 1,000 Pa |
| 1 psi | 6,894.757293 Pa |
| 1 bar | 100,000 Pa |
| 1 standard atmosphere (atm) | 101,325 Pa |
| 1 torr | 133.322368 Pa |
| 1 millimeter of mercury (mmHg) | Approximately 133.322 Pa |
| 1 megapascal (MPa) | 1,000,000 Pa |
Absolute Pressure vs Gauge Pressure
Absolute pressure is measured relative to a perfect vacuum. A reading of zero absolute pressure represents the absence of pressure.
Gauge pressure is measured relative to the surrounding atmospheric pressure. An ordinary tire-pressure gauge normally displays gauge pressure rather than absolute pressure.
The general relationship is:
Absolute pressure = Gauge pressure + Atmospheric pressure
At standard atmospheric pressure, a gauge pressure of 200 kPa corresponds to an absolute pressure of approximately 301.325 kPa.
Pressure units such as Pa, bar, and psi do not indicate the reference point by themselves. Labels such as psia and psig are sometimes used to distinguish absolute pressure from gauge pressure.
Which Pressure Unit Should You Use?
- Science and engineering: pascal, kilopascal, or megapascal.
- Weather and atmospheric pressure: hectopascal, millibar, or atmosphere.
- Tire pressure: psi, bar, or kilopascal.
- Hydraulic systems: bar, psi, or megapascal.
- Vacuum measurement: pascal, torr, millibar, or millimeter of mercury.
- Blood pressure: millimeter of mercury.
- Material strength: megapascal, gigapascal, or newton per square millimeter.
Always check whether a specification uses absolute or gauge pressure, especially when working with gases, vacuum systems, and engineering equipment.
When Are Pressure Conversions Used?
Pressure conversions are used in engineering, manufacturing, meteorology, aviation, automotive maintenance, medicine, hydraulics, pneumatics, refrigeration, vacuum technology, and scientific research.
For example, a tire specification may be given in psi while a pressure gauge displays bar, or a weather report may use hectopascals while another source uses millibars. Converting the measurements makes it possible to compare them accurately.
Pressure Conversion FAQ
What is the SI unit of pressure?
The SI-derived unit of pressure is the pascal. One pascal equals one newton of force applied over an area of one square meter: 1 Pa = 1 N/m².
How do I convert pressure units?
Convert the original measurement to pascals and then divide by the pascal value of the target unit. The online converter performs both operations automatically.
How many pascals are in one bar?
One bar equals exactly 100,000 pascals.
How many pascals are in one atmosphere?
One standard atmosphere equals exactly 101,325 pascals.
How many kilopascals are in one psi?
One psi is approximately equal to 6.894757 kilopascals.
Are hectopascals and millibars equal?
Yes. One hectopascal equals one millibar because both units equal 100 pascals.
Are torr and mmHg exactly the same?
They are extremely close but are defined differently. One torr is exactly 1/760 of a standard atmosphere, while a millimeter of mercury is based on the pressure produced by a mercury column under specified conditions.
Does psi mean absolute or gauge pressure?
The symbol psi only identifies the unit. The measurement context determines its reference. The labels psia and psig are commonly used for absolute and gauge pressure respectively.
Why can converted results differ slightly?
Some conversion factors produce long or repeating decimals. Calculators may display different results depending on how many decimal places they retain or how they round the final value.
Is this pressure converter free?
Yes. The pressure converter is available online without charge.
Pressure Unit Standards and References
The pascal and the SI system are maintained internationally by the International Bureau of Weights and Measures. Additional guidance about SI units and pressure conversions is available from: